Abstract
The phosphogypsum (PG) endogenous bacterial community and endophytic bacterial communities of four plants growing in phosphogypsum-contaminated sites, Suaeda fruticosa (SF), Suaeda mollis (SM), Mesembryanthmum nodiflorum (MN) and Arthrocnemum indicum (AI) were investigated by amplicon sequencing. Results highlight a more diverse community of phosphogypsum than plants associated endophytic communities. Additionally, the bacterial culturable communities of phosphogypsum and associated plant endophytes were isolated and their plant-growth promotion capabilities, bioremediation potential and stress tolerance studied. Most of plant endophytes were endowed with plant growth-promoting (PGP) activities and phosphogypsum communities and associated plants endophytes proved highly resistant to salt, metal and antibiotic stress. They also proved very active in bioremediation of phosphogypsum and other organic and inorganic environmental pollutants. Genome sequencing of five members of the phosphogypsum endogenous community showed that they belong to the recently described species Bacillus albus (BA). Genome mining of BA allowed the description of pollutant degradation and stress tolerance mechanisms. Prevalence of this tool box in the core, accessory and unique genome allowed to conclude that accessory and unique genomes are critical for the dynamics of strain acquisition of bioremediation abilities. Additionally, secondary metabolites (SM) active in bioremediation such as petrobactin have been characterized. Taken together, our results reveal hidden untapped valuable bacterial actors for waste remediation.
Highlights
When using rock phosphate as raw material for the production of phosphoric acid, phosphogypsum (PG) is the main waste generated
To unravel the potential of use of the phosphogypsum microbiome and the potential of endophytic plants thriving in this waste for its remediation, we investigated through cultivation independent phosphogypsum bacterial microbiome as well as bacterial endophyte microbiomes of four plants Suaeda fruticosa (SF), Suaeda mollis (SM), Mesembryanthmum nodiflorum (MN) and Arthrocnemum indicum (AI) thriving in this waste
The plants SF, SM, MN and AI endophytic microbiomes were dominated by protebacteria
Summary
When using rock phosphate as raw material for the production of phosphoric acid, phosphogypsum (PG) is the main waste generated. Phosphogypsum, currently considered a NORM (naturally occurring radioactive material), contains numerous hazardous materials such as natural radionuclides and heavy metals [1]. Management of phosphogypsum is challenging in numerous countries. In Tunisia, when discharged on the marine environment in the Gulf of Gabes, phosphogypsum severely impacts the ecosystem where environmental conditions can be considered as critical [2]. Its use as a fertilizer, while environmentally and economically sound, is hindered by its high toxicity to crops and earthworms [3,4,5,6]. There is an urgent need to remediate the millions of tons of PG that weaken ecosystem functions and represent serious threats to the environment and human health
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